New procedures for arsenic speciation: A review

Ionic Liquid Modified Polymer Gel for Arsenic Speciation

A new ionic liquid modified polymer gel containing methylimidazolium groups (poly(MIA)) is proposed as a sorbent for the separation and enrichment of trace inorganic and organic arsenic species in surface waters. The poly(MIA) was synthesized by chemical modification of polymeric precursor using post-polymerization modification of poly(glycidyl methacrylate-co-trimethylolpropane trimethacrylate). The composition, structure, morphology, and surface properties of the prepared particles were characterized using elemental analysis, Fourier transform infrared spectroscopy, scanning electron microscopy, and nitrogen adsorption-desorption measurements. Optimization experiments showed that at pH 8, monomethylarsonic acid (MMAs), dimethylarsinic acid (DMAs), and As(V) were completely retained on the poly(MIA), while the sorption of As(III) was insignificant. The desorption experiments revealed that due to the weaker binding of organic arsenic species, selective elution with 1 mol/L acetic acid for MMAs + DMAs, followed by elution with 2 mol/L hydrochloric acid for As(V), ensured their quantitative separation. The adsorption kinetic and mechanism were defined. The analytical procedure for As(III), As(V), MMAs, and DMAs determination in surface waters was developed and validated through the analysis of certified reference material.

Determination and speciation of arsenic in drinking water samples by X-ray spectrometry technique

Arsenic is ranked as the first compound in the Substance Priority List 2023 by the Agency for Toxic Substances and Disease Registry (ATSDR). The most prominent entrance to the human body is through drinking water wherein the predominant species are arsenite and arsenate. The more toxic As(III) has rigorously threatened human health worldwide; hence, speciation and separation are the need of the hour. In this article, we have reported a simple method of arsenic speciation by wavelength dispersive X-ray fluorescence (WD-XRF) spectrometer. Valence to core (VtC) electronic transitions, i.e., AsKβ2,5 fluorescence lines were used for arsenic speciation. This speciation study by WD-XRF entails direct measurement of activated alumina pellets containing arsenate and arsenite species adsorbed from water sample without separation of the trivalent and pentavalent species. This is the first report wherein the X-ray technique has been explored for speciation analysis of arsenic and the biggest advantage of the method lies in its applicability to direct analysis of synthesized nanotubes or other solid-phase extraction sorbents entrapping both the arsenic species. For determination of total arsenic using activated alumina as adsorbent, the most intense AsKα1,2 analytical lines were used and the instrumental limit of detection and the lower limit of quantification were 0.23 μg/L and 0.89 μg/L, respectively. For speciation, these limits were calculated to be 50 μg/L and 200 μg/L, respectively.

Shipboard determination of arsenite and total dissolved inorganic arsenic in estuarine and coastal waters with an automated on-site-applicable atomic fluorescence spectrometer

The speciation of trace level arsenic (As) in estuarine and coastal waters is crucial for both biogeochemical and toxicological studies of this toxic metalloid. However, the accurate and on-site determination of As in complex seawater matrices is challenging because of the low concentration of As, the easy conversion of arsenite (As(III)) to arsenate (As(V)), and the considerable effect of salinity on the determination of As via conventional methods. In this study, a custom-made shipboard atomic fluorescence spectrometer (AFS) is reported for the on-site speciation of inorganic As in estuarine and coastal waters. After comprehensive optimization of the instrumental and chemical parameters, the method demonstrated high sensitivity (limits of detection: 0.02 μg L-1), good linearity (R2 > 0.999 for all calibration curves up to 8 μg L-1), high precision (relative standard deviations (RSDs) of less than 2% at 1 μg L-1 over a year-long evaluation), and excellent performance for sample analysis for different matrices with varying salinities (recoveries: 96.3%-105.3%). The portable and field-applicable AFS was successfully applied to the on-site and shipboard simultaneous determination of As(III) and total dissolved inorganic arsenic (TDIAs) in the coastal waters of Shandong, Jiangsu, Zhejiang, Fujian, and Guangdong province of China, demonstrating its robustness and applicability in harsh conditions.

Arsenic Contamination in Groundwater: Geochemical Basis of Treatment Technologies

Arsenic (As) is abundant in the environment and can be found in both organic (e.g., methylated) and inorganic (e.g., arsenate and arsenite) forms. The source of As in the environment is attributed to both natural reactions and anthropogenic activities. As can also be released naturally to groundwater through As-bearing minerals including arsenopyrites, realgar, and orpiment. Similarly, agricultural and industrial activities have elevated As levels in groundwater. High levels of As in groundwater pose serious health risks and have been regulated in many developed and developing countries. In particular, the presence of inorganic forms of As in drinking water sources gained widespread attention due to their cellular and enzyme disruption activities. The research community has primarily focused on reviewing the natural occurrence and mobilization of As. Yet, As originating from anthropogenic activities, its mobility, and potential treatment techniques have not been covered. This review summarizes the origin, geochemistry, occurrence, mobilization, microbial interaction of natural and anthropogenic-As, and common remediation technologies for As removal from groundwater. In addition, As remediation methods are critically evaluated in terms of practical applicability at drinking water treatment plants, knowledge gaps, and future research needs. Finally, perspectives on As removal technologies and associated implementation limitations in developing countries and small communities are discussed.

Gold Nanoparticles as Exquisite Colorimetric Transducers for Water Pollutant Detection

Gold nanoparticles (AuNPs) are useful nanomaterials as transducers for colorimetric sensors because of their high extinction coefficient and ability to change color depending on aggregation status. Therefore, over the past few decades, AuNP-based colorimetric sensors have been widely applied in several environmental and biological applications, including the detection of water pollutants. According to various studies, water pollutants are classified into heavy metals or cationic metal ions, toxins, and pesticides. Notably, many researchers have been interested in AuNP that detect water pollutants with high sensitivity and selectivity, while offering no adverse environmental issues in terms of AuNP use. This review provides a representative overview of AuNP-based colorimetric sensors for detecting several water pollutants. In particular, we emphasize the advantages of AuNP as colorimetric transducers for water pollutant detection in terms of their low toxicity, high stability, facile processability, and unique optical properties. Next, we discuss the status quo and future prospects of AuNP-based colorimetric sensors for the detection of water pollutants. We believe that this review will promote research and development of AuNP as next-generation colorimetric transducers for water pollutant detection.

Characterization and Quantification of Arsenic Species in Foodstuffs of Plant Origin by HPLC/ICP-MS

Arsenic is a well-known carcinogenic, mutagenic and toxic element and occurs in the environment both as inorganic arsenic (iAs) and organoarsenical compounds (oAsCs). Since the toxicity of arsenic compounds depends on their chemical form, the identification and determination of arsenic species are essential. Recently, the European Food Safety Authority, following the European Commission request, published a report on chronic dietary exposure to iAs and recommended the development and validation of analytical methods with adequate sensitivity and refined extraction procedures for this determination. Moreover, the authority called upon new arsenic speciation data for complex food matrices such as seaweeds, grains and grain-based products. Looking at this context, an optimized, sensitive and fast analytical method using high performance liquid chromatography followed by inductively coupled plasma-mass spectrometry (HPLC/ICP-MS) was developed for the determination of iAs (sum of arsenite-As^III and arsenate-As^V) and the most relevant oAsCs, arsenobetaine, dimethylarsinic acid and monomethylarsonic acid. The method was validated with satisfactory results in terms of linearity, sensitivity, selectivity, precision, recovery, uncertainty, ruggedness and matrix effect, and then successfully applied for the analysis of several matrices, i.e., processed and unprocessed cereal and cereal products, fruits, vegetables, legumes, seaweeds, nuts and seeds. The results obtained indicate that not only seaweed and rice matrices but also many cereals, legumes and plant-based foods for infants and young children contain significant concentrations of iAs and oAsCs. These findings contribute to the data collection necessary to assess the role of these matrices in the total arsenic exposure and if specific maximum limits have to be established.

Carbon Nanomaterials-Based Electrochemical Sensors for Heavy Metal Detection

Heavy metals are commonly found in a wide range of environmental settings metals, but the potential toxicity associated with heavy metal exposure represents a major threat to global public health. It is thus vital that approaches to efficiently, reliably, and effectively detecting heavy metals in a range of sample types be established. Carbon nanomaterials offer many advantageous properties that make them well-suited to the design of sensitive, selective, easy-to-operate electrochemical biosensors ideal for detecting heavy metal ions. The present review offers an overview of recent progress in the development of carbon nanomaterial-based electrochemical sensors used to detect heavy metals. In addition to providing a detailed discussion of certain carbon nanomaterials such as carbon nanotubes, graphene, carbon fibers, carbon quantum dots, carbon nanospheres, mesoporous carbon, and Graphdiyne, we survey the challenges and future directions for this field. Overall, the studies discussed herein suggest that the further development of carbon nanomaterial-modified electrochemical sensors will support the integration of increasingly advanced sensor platforms to aid in detecting heavy metals in foods, environmental samples, and other settings, thereby benefitting human health and society as a whole.

Estimation of the Frequency and Time of Human Exposure to Arsenic by Single Hair Analysis

Arsenic (As) and its compounds are widely used in many applications. Long-term exposure to As can cause acute and chronic poisoning. In severe cases, it can lead to adverse effects, such as gene mutation, cell cancer and fetal malformation. The objective of this study was to accurately estimate As exposure frequency and time. Quantitative analysis of As in single hairs obtained from APL (acute promyelocytic leukemia) patients treated with As₂O₃ was performed by LA-ICP-MS. An informative As concentration distribution profile of single hair was applied to estimate the As exposure frequency and time. As exposure frequency was estimated according to the number of As concentration peaks. As exposure time was estimated according to the hair growth length in combination with the hair growth rate. The validation results demonstrate that this method was more efficient than the traditional method; compared with the traditional method, which provides estimates in months, our model shortened the As exposure time estimate to the range of a few days, which considerably improved the inference accuracy. Therefore, these results can be used for forensic toxicology studies, environmental exposure monitoring, etc.

Relevance of the microbial community to Sb and As biogeochemical cycling in natural wetlands

Mining activities lead to elevated levels of antimony (Sb) and arsenic (As) in river systems, having adverse effects on the aquatic environment and human health. Microbes inhabiting river sediment can mediate the transformation of Sb and As, thus changing the toxicity and mobility of Sb and As. Compared to river sediments, natural wetlands could introduce distinct geochemical conditions, leading to the formation of different sedimentary microbial compositions between river sediments and wetland sediments. However, whether such changes in microbial composition could influence the microbially mediated geochemical behavior of Sb or As remains poorly understood. In this study, we collected samples from a river contaminated by Sb tailings and a downstream natural wetland to study the influence of microorganisms on the geochemical behavior of Sb and As after the Sb/As-contaminated river entered the natural wetland. We found that the microbial compositions in the natural wetland soil differed from those in the river sediment. The Sb/As contaminant components (Sb(III), As(III), As(V), As_exe) and nutrients (TC) were important determinants of the difference in the compositions of the microbial communities in the two environments. Taxonomic groups were differentially enriched between the river sediment and wetland soil. For example, the taxonomic groups Xanthomonadales, Clostridiales and Desulfuromonadales were important in the wetland and were likely to involve in Sb/As reduction, sulfate reduction and Fe(III) reduction, whereas Burkholderiales, Desulfobacterales, Hydrogenophilales and Rhodocyclales were important taxonomic groups in the river sediments and were reported to involve in Sb/As oxidation and sulfide oxidation. Our results suggest that microorganisms in both river sediments and natural wetlands can affect the geochemical behavior of Sb/As, but the mechanisms of action are different.

A New Strategy for As(V) Biosensing Based on the Inhibition of the Phosphatase Activity of the Arsenate Reductase from Thermus thermophilus

Arsenic (As) pollution is a widespread problem worldwide. In recent years, biosensors based on enzymatic inhibition have been developed for arsenic detection, making the study of the effect of inhibitors on the selected enzymatic activity crucial for their setup. The arsenate reductase of Thermus thermophilus HB27, TtArsC, reduces As(V) into As(III), but is also endowed with phosphatase activity. This work investigates the inhibitory effects of As(V) and As(III) on phosphatase activity by taking advantage of a simple colorimetric assay; the results show that both of them are non-competitive inhibitors affecting the Vmax but not the K_M of the reaction. However, their Ki values are different from each other (15.2 ± 1.6 μM for As(V) and 394.4 ± 40.3 µm with As(III)), indicating a higher inhibitory effect by As(V). Moreover, the inhibition-based biosystem results to be selective for As(V) since several other metal ions and salts do not affect TtArsC phosphatase activity; it exhibits a sensitivity of 0.53 ± 0.03 mU/mg/μM and a limit of detection (LOD) of 0.28 ± 0.02 μM. The good sensitivity and specificity for As(V) point to consider inhibition of TtArsC phosphatase activity for the setup of a novel biosensor for the detection of As(V).

Ultrasensitive determination and non-chromatographic speciation of inorganic arsenic in foods and water by photochemical vapor generation-ICPMS using CdS/MIL-100(Fe) as adsorbent and photocatalyst

The determination of inorganic arsenic species in real samples can be particularly challenging due to their trace levels and the interferences arising from sample matrix. Normally, the speciation analysis necessitates chromatographic separation. Herein, we report a novel method for the ultrasensitive detection and non-chromatographic speciation of inorganic arsenic by inductively coupled plasma mass spectrometry (ICP-MS), utilizing CdS/MIL-100(Fe) composites as an adsorbent and photocatalyst. The synthesized CdS/MIL-100(Fe) could completely adsorb As(V) and As(III) within 5 and 105 min, respectively. Following filtration and re-suspension in formic acid, the adsorbed As(III)/As(V) were reduced to arsine (AsH₃) under UV irradiation and swept to ICP-MS for detection. The limits of detection were found to be 1.7 ng L^-1 (without preconcentration) and 0.11 ng L^-1 (after 20-fold preconcentration). The method was successfully applied to the determination of trace inorganic arsenic in various food and water samples.

Arsenic biogeochemical cycling in paddy soil-rice system: Interaction with various factors, amendments and mineral nutrients

Arsenic (As) contamination is a well-recognized environmental and health issue, threatening over 200 million people worldwide with the prime cases in South and Southeast Asian and Latin American countries. Rice is mostly cultivated under flooded paddy soil conditions, where As speciation and accumulation by rice plants is controlled by various geo-environmental (biotic and abiotic) factors. In contrast to other food crops, As uptake in rice has been found to be substantially higher due to the prevalence of highly mobile and toxic As species, arsenite (As(III)), under paddy soil conditions. In this review, we discussed the biogeochemical cycling of As in paddy soil-rice system, described the influence of critical factors such as pH, iron oxides, organic matter, microbial species, and pathways affecting As transformation and accumulation by rice. Moreover, we elucidated As interaction with organic and inorganic amendments and mineral nutrients. The review also elaborates on As (im)mobilization processes and As uptake by rice under the influence of different mineral nutrients and amendments in paddy soil conditions, as well as their role in mitigating As transfer to rice grain. This review article provides critical information on As contamination in paddy soil-rice system, which is important to develop suitable strategies and mitigation programs for limiting As exposure via rice crop, and meet the UN's key Sustainable Development Goals (SDGs: 2 (zero hunger), 3 (good health and well-being), 12 (responsible consumption and production), and 13 (climate action)).

Arsenic Content, Speciation, and Distribution in Wild Cordyceps sinensis

The excessive arsenic content in wild Cordyceps sinensis has caused great concerns on human health. The toxicity of arsenic depends on its concentration, chemical form, and valence. The source studies of arsenic in C. sinensis are essential for safety evolution and quality control. We used ICP-MS and HPLC-ICP-MS methods to determine the total arsenic amount and the arsenic speciation. Synchrotron-based XANES and micro-XRF imaging techniques were used to characterize arsenic valence and distribution. The total arsenic amount range in wild C. sinensis samples was 5.77–13.20 μg/g with an average of 8.85 ± 2.5 μg/g. As(III) and As(V) were the main species in wild C. sinensis samples. The iAs only accounts for 4.47–11.42% of the extracted arsenic. Trivalent and pentavalent forms were the dominant chemical forms of arsenic. Besides, we found that arsenic was accumulated at the digestive tract of the host larva.

Electrodialytic treatment of secondary mining resources for raw materials extraction: Reactor design assessment

The sustainability of mining activities is compromised due to the high amounts of mining residues generated that have to be disposed of, often in open dams, that may cause environmental deterioration, e.g. release of toxic elements to water supplies. These residues are, however, secondary resources of raw materials. In the case of Panasqueira mine, they even are a source of tungsten, considered a critical raw material. The present work aims to assess the electrodialytic process efficiency for raw materials extraction from Panasqueira mine residues. Experiments were performed with 2 and 3-compartment electrodialytic reactors, applying current intensities between 50 and 100 mA, from 4 to 14 days, and sample suspensions enhanced with NaCl or effluent. Additionally, control experiments with no current application were carried out. The results showed that a 3-compartment reactor operating at 100 mA, with NaCl as supporting electrolyte, presented the highest extraction of copper (13%), tin (10%), tungsten (13%) and arsenic (63%).

Determination of arsenic species using functionalized ionic liquid by in situ dispersive liquid-liquid microextraction followed by atomic absorption spectrometry

Synthesis and application of a task-specific ionic liquids (TSILs) as extracting solvents or chelating agents in dispersive liquid-liquid micro-extraction (DLLME) was evaluated. The developed method was based on the use of an ammonium pyrrolidine dithiocarbamate (APDC) bonded ionic liquid for chelation with As(III), followed by conversion of the As(III) chelated TSIL to a hydrophobic ionic liquid using KPF₆ as an anion-exchange reagent. As(V) was reduced to As(III), using a 2/1 w/w blend of KI and Na₂S₂O₃ and then the total amount of As was measured through ETAAS analysis. Under optimal conditions, linear dynamic ranges of 0.2-15 ng mL^-1 and 0.2-20 ng mL^-1 were observed in the determination of As(III) and total As respectively. The relative standard deviations (RSD%, n = 5) for the determination of As(III) (10 ng mL^-1) was 3.2% and the limits of detection and quantitation were determined to be 0.01 ng mL^-1 and 0.0.034 ng mL^-1; respectively.

Determination of four arsenic species in environmental water samples by liquid chromatography- inductively coupled plasma - tandem mass spectrometry

Robust and sensitive methods for monitoring inorganic and organic As species As(III), As(V), dimethylarsinate (DMA), and monomethylarsonate (MMA) in environmental water are necessary to understand the toxicity and redox processes of As in a specific environment. The method is sufficiently sensitive and selective to ensure accurate and precise quantitation of As(III), As(V), DMA, and MMA in surface water and groundwater samples with As species concentrations from tens of nanograms per liter to 50 µg/L without dilution of the sample. Mean recoveries of the four species spiked into reagent water, surface water and groundwater and measured periodically over three months ranged from 87.2 % to 108.7 % and relative standard deviation of replicates of all analytes ranged from 1.1 % to 9.0 %.•

A PRP-X100 column and nitrate/phosphate mobile phase was used to separate As(III), As(V), DMA, and MMA in 0.45 µm filtered surface water and groundwater matrices.

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Oxygen was used in the collision cell of the inductively coupled plasma-mass spectrometer with MS/MS mode to shift the measured As mass from 75 to 91.

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The analytical performance of the method and figures of merit including detection limits, precision, accuracy, and interferences when applied to surface water and groundwater matrices were investigated.

Differential distribution of and similar biochemical responses to different species of arsenic and antimony in Vetiveria zizanioides

Vetiver grass (Vetiveria zizanioides L. Nash) has a great application potential to the phytoremediation of heavy metals pollution. However, few studies explored the bioavailability and distribution of different speciations of As and Sb in V. zizanioides. This study aimed to clarify the allocation and accumulation of two inorganic species arsenic (As(III) and As(V)) and antimony (Sb(III) and Sb(V)) in V. zizanioides, to understand the self-defense mechanisms of V. zizanioides to these metal(loids) elements. Thus, an experiment was conducted under greenhouse conditions to identify distribution of As and Sb in plant roots and shoots. Antioxidant enzymes (superoxide dismutase, SOD) and changes of subcellular structures were tested to evaluate metal(loids) tolerance capacities of V. zizanioides. This study demonstrated that V. zizanioides had higher capacity to accumulate Sb than As. For Sb absorption, Sb(III) content is significantly higher than Sb(V) in tissues of V. zizanioides under all concentration levels, despite the oxidation of Sb(III) on the nutrient solution surface. Additional Sb was mainly accumulated in plant roots due to Sb immobilization by transforming it into precipitates. As was more easily transferred to aerial tissues and had low accumulation rates, probably due to its restricted uptake rather than restricted transport. In many cases, two inorganic species of As and Sb showed almost same biotoxicity to V. zizanioides estimated from its biomass, SOD activity, and MDA content as well as functional groups. In summary, the results of this study provide new insights into understanding allocation, accumulation and phytotoxicity effects of arsenic and antimony in V. zizanioides. Schematic diagram of distribution of and biochemical responses to As(III), As(V), Sb(III), and Sb(V) in tissue of V. zizanioides.

Speciation analysis of inorganic As and Sb in urban dust using slurry sampling and detection by fast sequential hydride generation atomic absorption spectrometry

In this work, a methodology for chemical speciation analysis of inorganic As and Sb in urban dust using slurry sampling and detection by fast sequential hydride generation atomic absorption spectrometry is proposed. Doehlert design and desirability function were used to find the optimum conditions for hydride generation (1.0 mol L^-1 HCl and 0.9% m v^-1 NaBH₄). The accuracy of the analytical method was evaluated by analysis of reference material fly ash (BCR 176R), addition and recovery tests for inorganic As species, and comparison of independent methods for Sb determination in urban dust samples. The determination of the total concentrations of As and Sb and their inorganic species presented good accuracy, between 80 ± 1 and 101 ± 6%. Precision was expressed as the relative standard deviation and was better than 4.7% (n = 3). The limit-of-quantification values were 0.23 and 1.03 mg kg^-1 for As and Sb, respectively. The methodology was applied to eight samples of dust collected in an urban area of Salvador and Jaguaquara cities, Bahia, Northeast, Brazil, with an aerodynamic size lower than 38 μm. Concentrations of pentavalent inorganic species (iAs⁵⁺ and iSb⁵⁺) in relation to trivalent species (iAs³⁺ and iSb³⁺) were found in urban dust collected in the city of Salvador, which are regarded as more toxic for both elements. The enrichment factor and geoaccumulation index (I_geo) values showed that for some samples, the concentrations of iAs and iSb presented strong enrichment and, and regarding environment, strong to moderately polluted by iAs and iSb, with an indication of anthropogenic contributions. The occurrence of these inorganic constituents in the urban area of Salvador can be related with intense industrial activities and vehicular traffic.

Recent Advances in Nanomaterials for Analysis of Trace Heavy Metals

In an effort to achieve high sensitivity analysis methods for ultra-trace levels of heavy metals, numerous new nanomaterials are explored for the application in preconcentration processes and sensing systems. Nanomaterial-based methods have proven to be effective for selective analysis and speciation of heavy metals in combination with spectrometric techniques. This review outlined the different types of nanomaterials applied in the field of heavy metal analysis, and concentrated on the latest developments in various new materials. In particular, the functionalization of traditional materials and the exploitation of bio-functional materials could increase the specificity to target metals. The hybridization of multiple materials could improve material properties, to build novel sensor system or achieve detection-removal integration. Finally, we discussed the future perspectives of nanomaterials in the heavy metal preconcentration and sensor design, as well as their respective advantages and challenges. Despite impressive progress and widespread attention, the development of new nanomaterials and nanotechnology is still hampered by numerous challenges, particularly in the specificity to the target and the anti-interference performance in complex matrices.

Trace Arsenic Determination in a TiO2 Pigment Matrix Using Electrothermal Atomic Absorption Spectrometry

This work describes the use of electrothermal atomic absorption spectrometry in combination with a pyrolytic graphite-coated tube with a platform for trace arsenic (As) determination in titanium dioxide (TiO₂) pigment. This type of matrix is challenging, as complete digestion in hydrofluoric acid-containing solution is needed. First, closed-vessel microwave digestion was performed for the full-sample decomposition. Next, a temperature program was optimized for drying, pyrolysis, and atomization temperatures. Furthermore, the use of a chemical modifier mixture was proposed that reduced the background contribution and prevented significant analyte loss and therefore improved the analytical procedure. The optimized method was validated for the detection (LOD) and quantification (LOQ) limits, the linear concentration range, accuracy, and precision. Special attention was devoted to the matrix-matching solutions in the calibration procedure. Linearity was confirmed in the 5.0 to 100.0 µg/L concentration range (R² = 0.999). The average recovery for 16 different real TiO₂ pigment samples was 92.0%, and the relative standard deviation value for six replicate measurements was ≤10.4%. Moreover, the LOD and LOQ in terms of the TiO₂ pigment mass was determined to be 0.2 µg/(g TiO₂) and 0.7 µg/(g TiO₂), respectively. The latter complies with Commission Directive 2008/128/EC, which does not allow more than 3 µg As/(g product) as the specific criteria of purity. Finally, based on scanning electron microscopy analysis of unused and several times used pyrolytic graphite-coated tubes, usage of the tube 250 times before replacement is recommended.

Selective speciation of inorganic arsenic in water using nanocomposite based solid-phase extraction followed by inductively coupled plasma-mass spectrometry detection

The multi-walled carbon nanotubes-branched polyethyleneimine (MWCNTs-BPEI) adsorbent composite material was employed to separate and pre-concentrate As(V) in water samples. The characterization of MWCNTs-BPEI by X-ray diffraction (XRD), thermogravimetric analysis (TGA), Fourier transform infrared (FTIR) spectroscopy and Raman spectroscopy showed successful modification of the composite. The MWCNTs-BPEI composite exhibited selective retention of As(V) in the presence of As(III) in water samples of pH 7 using 40 mg of composite as adsorbent. The pre-concentrated As(V) was quantified using inductively coupled plasma-mass spectrometry (ICP-MS). A limit of detection (LOD) of 0.0537 µg L^-1 and limit of quantification (LOQ) of 0.179 µg L^-1 were achieved along with pre-concentration factor of 23.3. A percentage recovery of 81.0% confirm the accuracy of the method. The As(V) concentrations in water were in the range of 0.0612-3.65 µg L^-1. The As(V) concentrations determined using solid-phase extraction (SPE) procedure were in good agreement with the concentrations obtained using high performance liquid chromatography hyphenated to inductively coupled mass-mass spectrometry (HPLC hyphenated to ICP-MS).

Occurrence, toxicity, and speciation analysis of arsenic in edible mushrooms

Owing to the strong concentration and biotransformation of arsenic, the influence of some edible mushrooms on human health has attracted widespread attention. The toxicity of arsenic greatly depends on its species, so the speciation analysis of arsenic is of critical importance. The aim of the present review is to highlight recent advances in arsenic speciation analysis in edible mushrooms. We summarized the contents and distribution of arsenic species in some edible mushrooms, the methods of sample preparation, and the techniques for their identification and quantification. Stability of the arsenic species during sample pretreatment and storage is also briefly discussed.

Arsenic concentrations and speciation in wild birds from an abandoned realgar mine in China

Birds are at a higher level in the food chain; however, the potential bioaccumulation and biotransformation of arsenic (As) in birds in As mines has rarely been studied. In this study, four passerine bird species (tree sparrow [Passer montanus], light-vented bulbul [Pycnonotus sinensis], Garrulax canorus [Leucodioptron canorus], and magpie [Pica pica]) were collected from an abandoned As mine in China. The highest recorded As concentrations were 4.95 mg/kg and 51.65 mg/kg in muscles and feathers, respectively. Detection using high-performance liquid chromatography inductively coupled plasma mass spectrometry (HPLC-ICP-MS) revealed six As species, including arsenite (As(III)), arsenate (As(V)), dimethylarsinic acid (DMA), monomethylarsonic acid (MMA), arsenobetaine (AsB) and arsenocholine (AsC), with the former three species as the dominant (>92%) and the latter three as the minor As species (<6.17%). Further analysis of the selected bird samples using the X-ray absorption near edge structure (XANES) technique revealed the existence of As(III)-tris-glutathione (As(III)-GSH), which can be regarded as equivalent to the non-extractable and unidentified As form in the HPLC-ICP-MS data. Both methods revealed similar patterns of As species in the birds from the As mine, with muscles containing mainly inorganic As and DMA and feathers containing mainly inorganic As. The results of this study contribute to the knowledge regarding As accumulation and speciation in terrestrial organisms.

Synergistic molecular assembly of an aptamer and surfactant on gold nanoparticles for the colorimetric detection of trace levels of As3+ ions in real samples

A facile and selective aptasensor was developed by the synergistic molecular assembly of the Ars-3 aptamer on AuNPs for the detection of As³⁺ ions using CTAB as a binder.

Inorganic Arsenic Determination in Food: A Review of Analytical Proposals and Quality Assessment Over the Last Six Years

Here we review recent developments in analytical proposals for the assessment of inorganic arsenic (iAs) content in food products. Interest in the determination of iAs in products for human consumption such as food commodities, wine, and seaweed among others is fueled by the wide recognition of its toxic effects on humans, even at low concentrations. Currently, the need for robust and reliable analytical methods is recognized by various international safety and health agencies, and by organizations in charge of establishing acceptable tolerance levels of iAs in food. This review summarizes the state of the art of analytical methods while highlighting tools for the assessment of quality assessment of the results, such as the production and evaluation of certified reference materials (CRMs) and the availability of specific proficiency testing (PT) programmes. Because the number of studies dedicated to the subject of this review has increased considerably over recent years, the sources consulted and cited here are limited to those from 2010 to the end of 2015.

Correlating microbial community profiles with geochemical conditions in a watershed heavily contaminated by an antimony tailing pond

Mining activities have introduced various pollutants to surrounding aquatic and terrestrial environments, causing adverse impacts to the environment. Indigenous microbial communities are responsible for the biogeochemical cycling of pollutants in diverse environments, indicating the potential for bioremediation of such pollutants. Antimony (Sb) has been extensively mined in China and Sb contamination in mining areas has been frequently encountered. To date, however, the microbial composition and structure in response to Sb contamination has remained overlooked. Sb and As frequently co-occur in sulfide-rich ores, and co-contamination of Sb and As is observed in some mining areas. We characterized, for the first time, the microbial community profiles and their responses to Sb and As pollution from a watershed heavily contaminated by Sb tailing pond in Southwest China. The indigenous microbial communities were profiled by high-throughput sequencing from 16 sediment samples (535,390 valid reads). The comprehensive geochemical data (specifically, physical-chemical properties and different Sb and As extraction fractions) were obtained from river water and sediments at different depths as well. Canonical correspondence analysis (CCA) demonstrated that a suite of in situ geochemical and physical factors significantly structured the overall microbial community compositions. Further, we found significant correlations between individual phylotypes (bacterial genera) and the geochemical fractions of Sb and As by Spearman rank correlation. A number of taxonomic groups were positively correlated with the Sb and As extractable fractions and various Sb and As species in sediment, suggesting potential roles of these phylotypes in Sb biogeochemical cycling.